The development of mobile construction cranes in ever-increasing sizes and greater degrees of sophistication has inevitably created certain mechanicl problems not found in smaller and more primitive cranes. In the largest cranes employing hydraulically operated telescoping booms, the axis of the boom pivot shaft has been raised to a point near the upper surface of the boom base section, thus allowing the major portion of the boom structure in the vertical plane to depend from the pivot shaft and nest between the two rising supports for the pivot shaft on the boom turntable. The arrangement is compact and very sturdy. The interior space within the boom base section immediately surrounding the pivot shaft is partly obstructed by an internal structural box member. Additionally, the interior space is utilized to house various accessory items which are required on the latest types of large telescoping boom cranes.
As a result, access to the interior end of the customary locking pin for the boom pivot shaft is difficult or impossible so that the locking pin cannot be hammered out of the cross opening in the pivot shaft when it is necessary to remove the pivot shaft in order to separate the boom from the turntable on a crane carrier.
This invention has for its main objective to solve this problem of boom pivot shaft locking pin removal in a safe and efficient manner where access to the interior end of the locking pin is difficult or impossible.
A further object of the invention is to utilize a locking pin receiver hub immediately surrounding the boom pivot shaft at the center of the shaft as an additional bearing support to resist deflection or bending of the pivot shaft.
Still another object of the invention is to provide a constraining means for the external nut which engages the screw-threaded extension of the locking pin which is constructed to allow a certain degree of lateral and angular adjustability of the locking pin and a certain degree of floating movement of the nut.
Another object and feature of the invention is the provision on the nut of a removable cross axis retainer pin for the threaded pivot shaft locking pin, thus preventing backing out of the locking pin due to vibration. The retainer pin cannot be inserted until the threaded locking pin is in the full lockingposition in the boom pivot shaft and thus forms a safety indicator to show that the pivot shaft is rigidly locked to the boom base section so that no relative rotation between these elements can occur.
Other features and advantages of the invention will become apparent during the course of the following detailed description.